I'm working on a friend's sh-3A, and have most of it working, except the vco output. I have a schematic from Roland, and I can trace the key voltage to the output of an op amp on the vco board, configured as a unity gain voltage follower. After that, I get lost. There is a matched transistor pair that gets the cv, which can be altered by adjusting the vco width and frequency pots or plugging in a vco pedal control. This pair eventually feeds a small board plugged into the vco board, and it is my guess that its output is a pulse that drives the LM3216 chip--the latter looks like an analog frequency divider that sends the 4', 8', 16' and 32' octaves to the vco octave sliders.

I'm not well-versed in discrete circuitry, so I'm not sure which components comprise the actual oscillator at this stage of the vco board. Can anyone with a knowledge of the sh 3 circuitry help me trace through this stage? BTW, I called National Semi and Sanyo, but they don't even show the LM3216 as a discontinued chip. I thought knowing the specs for the input to this chip would help me trace the vco circuitry preceding it. Is there any source of info on this chip, and possibly a supplier for a replacement in case I need to try a new one?

Thanks in advance.
Tony

I find a good source of info on discontinued chips is RS components. If you bug them (and you often have to be quite persistent), they can usually dig out the old data-sheets. They have archives of them going back to the '70's.

Hope this helps.

Ian